Surveyor s transit



(No Model.)

J A BROWN SURVEYORS TRANSIT.

No. 460,999. Patented ont. 6, 1891.

UNITED STATES PATENT OEEICE.

JAMES A. BROVN, OF VILMINGTON, OI-IIO.

SURVEYORS TRANSIT.

PECIFCATION forming part of Letters Patent No. 460,909, dated October 6,1891.

Application tiled April l1J 1891.

Serial No. 3 88,450. (No model.)

T0 all whom t may concern.-

Be it known that I, JAMES A. BROWN, a citizen of the United States,residing at filmington, in the county of Clinton and State of Ohio, haveinvented certain new and useful Improvements inIievel-Tubes forSurveying-Instruments; and Ido hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

My invention relates to theodolites, transits, levels, and other similarinstruments used in surveying; and it consists ot' a certain simplifiedconstruction for leveling` the saine, which will be hereinafterdescribed and claimed.

Reference is had to the accom pan ying drawings, wherein the same partsare indicated by the same letters. y

Figure l represents a perspective view of a surveyors theodolite fittedwith my improved level-tube. Fig. 2 represents a profile view of myimproved level-tube partly in section. Fig. 3 represents a plan view ofone form of level-scale.

A represents the telescope of the theodolite or transit mounted asusual. l

I3 represents a long level tube, preferably of brass, secured to thesaid telescope A and parallel to the line of sight. In the interiorof B,I havea long glass bubble-tube B,secured in the usual way. At the topand bottom of long brass tube 13,1 have two central slots to show thebubble h, and over each otl these slots I have a graduated scale F toindicate when the bubble b is in a central position. The brass tube Bhas fiat arms b', which slip over the screws C rigidly attached to thetelescope of the theodolite. The said arms b are held between nuts D,which are adj usted with capstan-bars tittin g in the holes (l. Thefunction of the double slot in the tube Il is to pr0- videa meansforleveling the instrument when the barrel is revolved verticallythrough one hundred and eighty degrees, thus providing against thenecessity for using two level-tubes, one above and one below the barrelof theinstrument, or of unclamping the plates. This is speciallydesirable when leveling work is being done.

Owing to inequalities in the wyes orin the glass tube, scale, or otherparts of the instru ment, the central position of the bubble when theinstrument is level and the bubble tube under it, as shown in thedrawings, is not necessarily in the same vertical line with the centralposition of the bubble when the instrument is level and the bubble-tubeover it. In other words, the two scalesF must each be independentlyadjusted foreach instrument. This would first be done at the instrument,makers, as follows: Fasten the glass bubbletube firmly in the long brasstube and rigidly fix a scale over the upper slot. Attach the long tubeto the telescope and in the ordinary way make it parallel to the line ofcollimation. The bubble now being in the center ot the scale, carefullyobserve the height on a leveling-rod. Turn the telescope verticallythrough one hundred and eighty degrees and the upper parts ot' theinstrument one-halt way around. The bubble is now in the opposite slot.Clamp the axis of the telescope and bring the horizontal cross-line tothe observed height, carefully mark the position of the bubble, andplace over it a scale, whose zeroline stands over its central point.This scale may be rigid or movable longitudinally, as shown in Fig. 3,where F represents the scale, and f slots for longitudinal adjustment.

The adjustment: Carefully level the plates, bring the bubble to thecenter of one of the scales, and observe the height on a levelingrod,turn thev telescope vertically through one hundred and eighty degreesand the upper parts of the instrument one-half way around, bring thebu-bble to the center of this Opposite scale, and again observe theheight on the rod. It the two heights are the same the long tube is inadjustment. It' not the same turn the horizontal cross-line on a point4midway between the two observed heights, clamp the telescope in thisposition, and by means of the capstannuts bring the bubble to the centerot' the scale, which completes the adjustment.

I am aware that two tubes have been em ployed to do the work ot' the oneinvented by me; but I claim that the use of a single tube with slots oneither side for the bubble not only simplifies the construction anddimin- IOO ishes the cost of the instrument, but it also cured theretoparallel to the line ot' sight, saidlevel-tube having upper and lowerslots with a scale on each slot for the bubble, substan tially asdescribed.

2. In an instrument for surveying, the cornbin ation, with a telescope,of a leveltubecon nected to the said telescope by screws rigidlyattached to the telescope, said tube having arms held between nutsmoving on the said screws and having upper and lower slots for the.bubble with adjustable scales fitted to each slot,-substantially asdescribed.

3. In a theodolite, the combination, with the telescope A, having screwsO rigidly secured thereto, of the tube B, inelosing a glass bubble-,tubeB', said tube B havingopposite apertures B2 and B3 for the bubble andarms b and b', slipping over the screws C, scales F, having elongatedapertures f for the screws f', secured over said apertures, and nuts D,holding said arms b', substantially as described.

.In testimony whereof I affix my signature in presence of two witnesses.

JAMES A. BROVN.

Witnesses:

MARY B. GLASS, EGBERT B. HOWLAND.

